1. Field of the invention
The invention relates to a method for initiating protective measures on rapidly running rotary machines upon the occurrence of impermissible vibrations, the vibrations or values derived therefrom essentially being measured as measured variables at the bearings of the rotors.
2. Discussion of Background
In known methods for protecting rapidly running rotary machines in which impermissible vibrations can occur which can destroy the installation, the result being the need to change the operating state as required or in a plannable fashion by means of monitoring signals, the vibration amplitudes or their maximum value are mostly measured in the region of the rotor bearings and compared with prescribed limits for alarm measures or emergency measures. If these limit values are exceeded, monitoring signals are generated as a function of these limit values which set the installation to a different rotational speed, for example, or shut it down completely. In this case, the measuring points can be arranged at a plurality of different sites in the installation, and the data can be processed at the same time. Thus, it is also possible to make use for evaluation of only two of three measured data.
Depending on the particular features and the frequently changing environmental conditions of the installation, however, the limit values fixed in advance can be inappropriate and set off false alarms. Such false alarms, in particular when they are associated with emergency shutdowns, cause a very substantial outlay on restarting and other additional costs, which should be avoided as far as possible. In particular, these limit values cannot be fixed uniquely for technical reasons alone, since, for example, they depend on the duration of a specific operating state, for example the start up state, the degree of warming, generally connected thereto, etc., and fluctuate strongly in many cases. Taking account also of measured data which change in such a way involves a high outlay on equipment and processing, and the aim is to make the monitoring as simple as possible. In particular, because the monitoring units can also fail or must be provided in a fashion which is fail-safe or redundant. Moreover, almost all disturbances which require a protective shutdown caused by vibrations occur suddenly. For this reason, a temporary increase in the limit values in the case of such transitional operating states poses a high risk to the installation. For example, if a blade breakage occurred on a turbo-machine precisely in such a phase, the machine might not shutdown, and further, secondary damage could be entailed.